Abstract:
A previously identified difficulty with the development of latent fingerprints on low-density polyethylene (LDPE) by
vacuum metal deposition (VMD) is that excess gold deposition prevents effective zinc deposition and so inhibits latent print
development [1]. The investigation of a means to correct for excess gold deposition was the basis for this study. Exposure to
zinc and the readmission of air into the vacuum chamber followed by VMD development results in the deactivation of the
initial gold clusters due to the formation of zinc oxide and the adsorption of air and water molecules. As a result, the majority
of the gold deposited during the second treatment creates new gold clusters rather than adding to the gold clusters previously
formed. After excess gold deposition on LDPE, the deposition of 1.5 times the optimum gold amount will result in goodquality
normal development. The results also indicate that, on all surfaces, at least twice the initial gold count should be used
for re-treatrnent when further development is required after air has been readmitted to the chamber.
